Synthesis, Characterization, and Catalytic Applications\nof Core–Shell Magnetic Carbonaceous Nanocomposites

Abstract

Magnetic\nresorcinol/formaldehyde resin (RF) and silica/RF nanocomposites\nwith well-defined core–shell architecture and tunable structural\nparameters had been prepared via the extended Stöber method.\nThe carbon counterparts with similar structure and morphology can\nbe obtained by thermal-treating the polymer precursors under N₂ atmosphere. The prepared materials were characterized by\nX-ray diffraction, transmission electron microscopy, scanning electron\nmicroscopy, Mössbauer spectroscopy, N₂ physical\nadsorption/desorption, and thermogravimetric analysis. The catalytic\napplications of the synthesized magnetic nanocomposites were also\nexplored. It has been shown that the magnetite core was oxidized to\nγ-Fe₂O₃ during polymer coating process\nand further reduced to original Fe₃O₄ phase\nduring carbonization. In addition, the iron oxide core can react with\nthe shell when carbonization temperature reaches 700 °C. The\nstructural stability of magnetic silica/RF is superior to magnetic\nRF because of the existence of an inner silica shell. Through a simple\ndeposition–precipitate method, active platinum nanoparticles\ncan be loaded in high dispersity onto the surface of the nanocomposites.\nThe constructed magnetic catalysts are very active in hydrogenation\nof nitroarenes to corresponding amines and can be separated facilely\nwith an external magnetic field.